/*
- * Copyright (c) 2004-2005 The Regents of The University of Michigan
+ * Copyright (c) 2010-2018 ARM Limited
+ * All rights reserved.
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder. You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Copyright (c) 2002-2005 The Regents of The University of Michigan
+ * Copyright (c) 2010,2015 Advanced Micro Devices, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Erik Hallnor
+ * Dave Greene
+ * Nathan Binkert
* Steve Reinhardt
- * Lisa Hsu
- * Kevin Lim
+ * Ron Dreslinski
+ * Andreas Sandberg
+ * Nikos Nikoleris
*/
/**
* @file
- * Cache template instantiations.
+ * Cache definitions.
*/
-#include "mem/config/cache.hh"
+#include "mem/cache/cache.hh"
-#if defined(USE_CACHE_LRU)
-#include "mem/cache/tags/lru.hh"
-#endif
+#include <cassert>
-#if defined(USE_CACHE_FALRU)
-#include "mem/cache/tags/fa_lru.hh"
-#endif
+#include "base/compiler.hh"
+#include "base/logging.hh"
+#include "base/trace.hh"
+#include "base/types.hh"
+#include "debug/Cache.hh"
+#include "debug/CacheTags.hh"
+#include "debug/CacheVerbose.hh"
+#include "enums/Clusivity.hh"
+#include "mem/cache/blk.hh"
+#include "mem/cache/mshr.hh"
+#include "mem/cache/tags/base.hh"
+#include "mem/cache/write_queue_entry.hh"
+#include "mem/request.hh"
+#include "params/Cache.hh"
-#if defined(USE_CACHE_IIC)
-#include "mem/cache/tags/iic.hh"
-#endif
+Cache::Cache(const CacheParams *p)
+ : BaseCache(p, p->system->cacheLineSize()),
+ doFastWrites(true)
+{
+}
-#if defined(USE_CACHE_SPLIT)
-#include "mem/cache/tags/split.hh"
-#endif
+void
+Cache::satisfyRequest(PacketPtr pkt, CacheBlk *blk,
+ bool deferred_response, bool pending_downgrade)
+{
+ BaseCache::satisfyRequest(pkt, blk);
-#if defined(USE_CACHE_SPLIT_LIFO)
-#include "mem/cache/tags/split_lifo.hh"
-#endif
+ if (pkt->isRead()) {
+ // determine if this read is from a (coherent) cache or not
+ if (pkt->fromCache()) {
+ assert(pkt->getSize() == blkSize);
+ // special handling for coherent block requests from
+ // upper-level caches
+ if (pkt->needsWritable()) {
+ // sanity check
+ assert(pkt->cmd == MemCmd::ReadExReq ||
+ pkt->cmd == MemCmd::SCUpgradeFailReq);
+ assert(!pkt->hasSharers());
-#include "mem/cache/cache_impl.hh"
+ // if we have a dirty copy, make sure the recipient
+ // keeps it marked dirty (in the modified state)
+ if (blk->isDirty()) {
+ pkt->setCacheResponding();
+ blk->status &= ~BlkDirty;
+ }
+ } else if (blk->isWritable() && !pending_downgrade &&
+ !pkt->hasSharers() &&
+ pkt->cmd != MemCmd::ReadCleanReq) {
+ // we can give the requester a writable copy on a read
+ // request if:
+ // - we have a writable copy at this level (& below)
+ // - we don't have a pending snoop from below
+ // signaling another read request
+ // - no other cache above has a copy (otherwise it
+ // would have set hasSharers flag when
+ // snooping the packet)
+ // - the read has explicitly asked for a clean
+ // copy of the line
+ if (blk->isDirty()) {
+ // special considerations if we're owner:
+ if (!deferred_response) {
+ // respond with the line in Modified state
+ // (cacheResponding set, hasSharers not set)
+ pkt->setCacheResponding();
-// Template Instantiations
-#ifndef DOXYGEN_SHOULD_SKIP_THIS
+ // if this cache is mostly inclusive, we
+ // keep the block in the Exclusive state,
+ // and pass it upwards as Modified
+ // (writable and dirty), hence we have
+ // multiple caches, all on the same path
+ // towards memory, all considering the
+ // same block writable, but only one
+ // considering it Modified
+ // we get away with multiple caches (on
+ // the same path to memory) considering
+ // the block writeable as we always enter
+ // the cache hierarchy through a cache,
+ // and first snoop upwards in all other
+ // branches
+ blk->status &= ~BlkDirty;
+ } else {
+ // if we're responding after our own miss,
+ // there's a window where the recipient didn't
+ // know it was getting ownership and may not
+ // have responded to snoops correctly, so we
+ // have to respond with a shared line
+ pkt->setHasSharers();
+ }
+ }
+ } else {
+ // otherwise only respond with a shared copy
+ pkt->setHasSharers();
+ }
+ }
+ }
+}
-#if defined(USE_CACHE_FALRU)
-template class Cache<FALRU>;
-#endif
+/////////////////////////////////////////////////////
+//
+// Access path: requests coming in from the CPU side
+//
+/////////////////////////////////////////////////////
-#if defined(USE_CACHE_IIC)
-template class Cache<IIC>;
-#endif
+bool
+Cache::access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
+ PacketList &writebacks)
+{
-#if defined(USE_CACHE_LRU)
-template class Cache<LRU>;
-#endif
+ if (pkt->req->isUncacheable()) {
+ assert(pkt->isRequest());
-#if defined(USE_CACHE_SPLIT)
-template class Cache<Split>;
-#endif
+ chatty_assert(!(isReadOnly && pkt->isWrite()),
+ "Should never see a write in a read-only cache %s\n",
+ name());
+
+ DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
+
+ // flush and invalidate any existing block
+ CacheBlk *old_blk(tags->findBlock(pkt->getAddr(), pkt->isSecure()));
+ if (old_blk && old_blk->isValid()) {
+ evictBlock(old_blk, writebacks);
+ }
+
+ blk = nullptr;
+ // lookupLatency is the latency in case the request is uncacheable.
+ lat = lookupLatency;
+ return false;
+ }
+
+ return BaseCache::access(pkt, blk, lat, writebacks);
+}
+
+void
+Cache::doWritebacks(PacketList& writebacks, Tick forward_time)
+{
+ while (!writebacks.empty()) {
+ PacketPtr wbPkt = writebacks.front();
+ // We use forwardLatency here because we are copying writebacks to
+ // write buffer.
+
+ // Call isCachedAbove for Writebacks, CleanEvicts and
+ // WriteCleans to discover if the block is cached above.
+ if (isCachedAbove(wbPkt)) {
+ if (wbPkt->cmd == MemCmd::CleanEvict) {
+ // Delete CleanEvict because cached copies exist above. The
+ // packet destructor will delete the request object because
+ // this is a non-snoop request packet which does not require a
+ // response.
+ delete wbPkt;
+ } else if (wbPkt->cmd == MemCmd::WritebackClean) {
+ // clean writeback, do not send since the block is
+ // still cached above
+ assert(writebackClean);
+ delete wbPkt;
+ } else {
+ assert(wbPkt->cmd == MemCmd::WritebackDirty ||
+ wbPkt->cmd == MemCmd::WriteClean);
+ // Set BLOCK_CACHED flag in Writeback and send below, so that
+ // the Writeback does not reset the bit corresponding to this
+ // address in the snoop filter below.
+ wbPkt->setBlockCached();
+ allocateWriteBuffer(wbPkt, forward_time);
+ }
+ } else {
+ // If the block is not cached above, send packet below. Both
+ // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
+ // reset the bit corresponding to this address in the snoop filter
+ // below.
+ allocateWriteBuffer(wbPkt, forward_time);
+ }
+ writebacks.pop_front();
+ }
+}
+
+void
+Cache::doWritebacksAtomic(PacketList& writebacks)
+{
+ while (!writebacks.empty()) {
+ PacketPtr wbPkt = writebacks.front();
+ // Call isCachedAbove for both Writebacks and CleanEvicts. If
+ // isCachedAbove returns true we set BLOCK_CACHED flag in Writebacks
+ // and discard CleanEvicts.
+ if (isCachedAbove(wbPkt, false)) {
+ if (wbPkt->cmd == MemCmd::WritebackDirty ||
+ wbPkt->cmd == MemCmd::WriteClean) {
+ // Set BLOCK_CACHED flag in Writeback and send below,
+ // so that the Writeback does not reset the bit
+ // corresponding to this address in the snoop filter
+ // below. We can discard CleanEvicts because cached
+ // copies exist above. Atomic mode isCachedAbove
+ // modifies packet to set BLOCK_CACHED flag
+ memSidePort.sendAtomic(wbPkt);
+ }
+ } else {
+ // If the block is not cached above, send packet below. Both
+ // CleanEvict and Writeback with BLOCK_CACHED flag cleared will
+ // reset the bit corresponding to this address in the snoop filter
+ // below.
+ memSidePort.sendAtomic(wbPkt);
+ }
+ writebacks.pop_front();
+ // In case of CleanEvicts, the packet destructor will delete the
+ // request object because this is a non-snoop request packet which
+ // does not require a response.
+ delete wbPkt;
+ }
+}
+
+
+void
+Cache::recvTimingSnoopResp(PacketPtr pkt)
+{
+ DPRINTF(Cache, "%s for %s\n", __func__, pkt->print());
+
+ // determine if the response is from a snoop request we created
+ // (in which case it should be in the outstandingSnoop), or if we
+ // merely forwarded someone else's snoop request
+ const bool forwardAsSnoop = outstandingSnoop.find(pkt->req) ==
+ outstandingSnoop.end();
+
+ if (!forwardAsSnoop) {
+ // the packet came from this cache, so sink it here and do not
+ // forward it
+ assert(pkt->cmd == MemCmd::HardPFResp);
+
+ outstandingSnoop.erase(pkt->req);
+
+ DPRINTF(Cache, "Got prefetch response from above for addr "
+ "%#llx (%s)\n", pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
+ recvTimingResp(pkt);
+ return;
+ }
+
+ // forwardLatency is set here because there is a response from an
+ // upper level cache.
+ // To pay the delay that occurs if the packet comes from the bus,
+ // we charge also headerDelay.
+ Tick snoop_resp_time = clockEdge(forwardLatency) + pkt->headerDelay;
+ // Reset the timing of the packet.
+ pkt->headerDelay = pkt->payloadDelay = 0;
+ memSidePort.schedTimingSnoopResp(pkt, snoop_resp_time);
+}
+
+void
+Cache::promoteWholeLineWrites(PacketPtr pkt)
+{
+ // Cache line clearing instructions
+ if (doFastWrites && (pkt->cmd == MemCmd::WriteReq) &&
+ (pkt->getSize() == blkSize) && (pkt->getOffset(blkSize) == 0)) {
+ pkt->cmd = MemCmd::WriteLineReq;
+ DPRINTF(Cache, "packet promoted from Write to WriteLineReq\n");
+ }
+}
+
+void
+Cache::handleTimingReqHit(PacketPtr pkt, CacheBlk *blk, Tick request_time)
+{
+ // should never be satisfying an uncacheable access as we
+ // flush and invalidate any existing block as part of the
+ // lookup
+ assert(!pkt->req->isUncacheable());
+
+ BaseCache::handleTimingReqHit(pkt, blk, request_time);
+}
+
+void
+Cache::handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk, Tick forward_time,
+ Tick request_time)
+{
+ if (pkt->req->isUncacheable()) {
+ // ignore any existing MSHR if we are dealing with an
+ // uncacheable request
+
+ // should have flushed and have no valid block
+ assert(!blk || !blk->isValid());
+
+ mshr_uncacheable[pkt->cmdToIndex()][pkt->req->masterId()]++;
+
+ if (pkt->isWrite()) {
+ allocateWriteBuffer(pkt, forward_time);
+ } else {
+ assert(pkt->isRead());
+
+ // uncacheable accesses always allocate a new MSHR
+
+ // Here we are using forward_time, modelling the latency of
+ // a miss (outbound) just as forwardLatency, neglecting the
+ // lookupLatency component.
+ allocateMissBuffer(pkt, forward_time);
+ }
+
+ return;
+ }
+
+ Addr blk_addr = pkt->getBlockAddr(blkSize);
+
+ MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
+
+ // Software prefetch handling:
+ // To keep the core from waiting on data it won't look at
+ // anyway, send back a response with dummy data. Miss handling
+ // will continue asynchronously. Unfortunately, the core will
+ // insist upon freeing original Packet/Request, so we have to
+ // create a new pair with a different lifecycle. Note that this
+ // processing happens before any MSHR munging on the behalf of
+ // this request because this new Request will be the one stored
+ // into the MSHRs, not the original.
+ if (pkt->cmd.isSWPrefetch()) {
+ assert(pkt->needsResponse());
+ assert(pkt->req->hasPaddr());
+ assert(!pkt->req->isUncacheable());
+
+ // There's no reason to add a prefetch as an additional target
+ // to an existing MSHR. If an outstanding request is already
+ // in progress, there is nothing for the prefetch to do.
+ // If this is the case, we don't even create a request at all.
+ PacketPtr pf = nullptr;
+
+ if (!mshr) {
+ // copy the request and create a new SoftPFReq packet
+ RequestPtr req = std::make_shared<Request>(pkt->req->getPaddr(),
+ pkt->req->getSize(),
+ pkt->req->getFlags(),
+ pkt->req->masterId());
+ pf = new Packet(req, pkt->cmd);
+ pf->allocate();
+ assert(pf->getAddr() == pkt->getAddr());
+ assert(pf->getSize() == pkt->getSize());
+ }
+
+ pkt->makeTimingResponse();
+
+ // request_time is used here, taking into account lat and the delay
+ // charged if the packet comes from the xbar.
+ cpuSidePort.schedTimingResp(pkt, request_time, true);
+
+ // If an outstanding request is in progress (we found an
+ // MSHR) this is set to null
+ pkt = pf;
+ }
+
+ BaseCache::handleTimingReqMiss(pkt, mshr, blk, forward_time, request_time);
+}
+
+void
+Cache::recvTimingReq(PacketPtr pkt)
+{
+ DPRINTF(CacheTags, "%s tags:\n%s\n", __func__, tags->print());
-#if defined(USE_CACHE_SPLIT_LIFO)
-template class Cache<SplitLIFO>;
+ promoteWholeLineWrites(pkt);
+
+ if (pkt->cacheResponding()) {
+ // a cache above us (but not where the packet came from) is
+ // responding to the request, in other words it has the line
+ // in Modified or Owned state
+ DPRINTF(Cache, "Cache above responding to %s: not responding\n",
+ pkt->print());
+
+ // if the packet needs the block to be writable, and the cache
+ // that has promised to respond (setting the cache responding
+ // flag) is not providing writable (it is in Owned rather than
+ // the Modified state), we know that there may be other Shared
+ // copies in the system; go out and invalidate them all
+ assert(pkt->needsWritable() && !pkt->responderHadWritable());
+
+ // an upstream cache that had the line in Owned state
+ // (dirty, but not writable), is responding and thus
+ // transferring the dirty line from one branch of the
+ // cache hierarchy to another
+
+ // send out an express snoop and invalidate all other
+ // copies (snooping a packet that needs writable is the
+ // same as an invalidation), thus turning the Owned line
+ // into a Modified line, note that we don't invalidate the
+ // block in the current cache or any other cache on the
+ // path to memory
+
+ // create a downstream express snoop with cleared packet
+ // flags, there is no need to allocate any data as the
+ // packet is merely used to co-ordinate state transitions
+ Packet *snoop_pkt = new Packet(pkt, true, false);
+
+ // also reset the bus time that the original packet has
+ // not yet paid for
+ snoop_pkt->headerDelay = snoop_pkt->payloadDelay = 0;
+
+ // make this an instantaneous express snoop, and let the
+ // other caches in the system know that the another cache
+ // is responding, because we have found the authorative
+ // copy (Modified or Owned) that will supply the right
+ // data
+ snoop_pkt->setExpressSnoop();
+ snoop_pkt->setCacheResponding();
+
+ // this express snoop travels towards the memory, and at
+ // every crossbar it is snooped upwards thus reaching
+ // every cache in the system
+ bool M5_VAR_USED success = memSidePort.sendTimingReq(snoop_pkt);
+ // express snoops always succeed
+ assert(success);
+
+ // main memory will delete the snoop packet
+
+ // queue for deletion, as opposed to immediate deletion, as
+ // the sending cache is still relying on the packet
+ pendingDelete.reset(pkt);
+
+ // no need to take any further action in this particular cache
+ // as an upstram cache has already committed to responding,
+ // and we have already sent out any express snoops in the
+ // section above to ensure all other copies in the system are
+ // invalidated
+ return;
+ }
+
+ BaseCache::recvTimingReq(pkt);
+}
+
+PacketPtr
+Cache::createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
+ bool needsWritable) const
+{
+ // should never see evictions here
+ assert(!cpu_pkt->isEviction());
+
+ bool blkValid = blk && blk->isValid();
+
+ if (cpu_pkt->req->isUncacheable() ||
+ (!blkValid && cpu_pkt->isUpgrade()) ||
+ cpu_pkt->cmd == MemCmd::InvalidateReq || cpu_pkt->isClean()) {
+ // uncacheable requests and upgrades from upper-level caches
+ // that missed completely just go through as is
+ return nullptr;
+ }
+
+ assert(cpu_pkt->needsResponse());
+
+ MemCmd cmd;
+ // @TODO make useUpgrades a parameter.
+ // Note that ownership protocols require upgrade, otherwise a
+ // write miss on a shared owned block will generate a ReadExcl,
+ // which will clobber the owned copy.
+ const bool useUpgrades = true;
+ if (cpu_pkt->cmd == MemCmd::WriteLineReq) {
+ assert(!blkValid || !blk->isWritable());
+ // forward as invalidate to all other caches, this gives us
+ // the line in Exclusive state, and invalidates all other
+ // copies
+ cmd = MemCmd::InvalidateReq;
+ } else if (blkValid && useUpgrades) {
+ // only reason to be here is that blk is read only and we need
+ // it to be writable
+ assert(needsWritable);
+ assert(!blk->isWritable());
+ cmd = cpu_pkt->isLLSC() ? MemCmd::SCUpgradeReq : MemCmd::UpgradeReq;
+ } else if (cpu_pkt->cmd == MemCmd::SCUpgradeFailReq ||
+ cpu_pkt->cmd == MemCmd::StoreCondFailReq) {
+ // Even though this SC will fail, we still need to send out the
+ // request and get the data to supply it to other snoopers in the case
+ // where the determination the StoreCond fails is delayed due to
+ // all caches not being on the same local bus.
+ cmd = MemCmd::SCUpgradeFailReq;
+ } else {
+ // block is invalid
+
+ // If the request does not need a writable there are two cases
+ // where we need to ensure the response will not fetch the
+ // block in dirty state:
+ // * this cache is read only and it does not perform
+ // writebacks,
+ // * this cache is mostly exclusive and will not fill (since
+ // it does not fill it will have to writeback the dirty data
+ // immediately which generates uneccesary writebacks).
+ bool force_clean_rsp = isReadOnly || clusivity == Enums::mostly_excl;
+ cmd = needsWritable ? MemCmd::ReadExReq :
+ (force_clean_rsp ? MemCmd::ReadCleanReq : MemCmd::ReadSharedReq);
+ }
+ PacketPtr pkt = new Packet(cpu_pkt->req, cmd, blkSize);
+
+ // if there are upstream caches that have already marked the
+ // packet as having sharers (not passing writable), pass that info
+ // downstream
+ if (cpu_pkt->hasSharers() && !needsWritable) {
+ // note that cpu_pkt may have spent a considerable time in the
+ // MSHR queue and that the information could possibly be out
+ // of date, however, there is no harm in conservatively
+ // assuming the block has sharers
+ pkt->setHasSharers();
+ DPRINTF(Cache, "%s: passing hasSharers from %s to %s\n",
+ __func__, cpu_pkt->print(), pkt->print());
+ }
+
+ // the packet should be block aligned
+ assert(pkt->getAddr() == pkt->getBlockAddr(blkSize));
+
+ pkt->allocate();
+ DPRINTF(Cache, "%s: created %s from %s\n", __func__, pkt->print(),
+ cpu_pkt->print());
+ return pkt;
+}
+
+
+Cycles
+Cache::handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
+ PacketList &writebacks)
+{
+ // deal with the packets that go through the write path of
+ // the cache, i.e. any evictions and writes
+ if (pkt->isEviction() || pkt->cmd == MemCmd::WriteClean ||
+ (pkt->req->isUncacheable() && pkt->isWrite())) {
+ Cycles latency = ticksToCycles(memSidePort.sendAtomic(pkt));
+
+ // at this point, if the request was an uncacheable write
+ // request, it has been satisfied by a memory below and the
+ // packet carries the response back
+ assert(!(pkt->req->isUncacheable() && pkt->isWrite()) ||
+ pkt->isResponse());
+
+ return latency;
+ }
+
+ // only misses left
+
+ PacketPtr bus_pkt = createMissPacket(pkt, blk, pkt->needsWritable());
+
+ bool is_forward = (bus_pkt == nullptr);
+
+ if (is_forward) {
+ // just forwarding the same request to the next level
+ // no local cache operation involved
+ bus_pkt = pkt;
+ }
+
+ DPRINTF(Cache, "%s: Sending an atomic %s\n", __func__,
+ bus_pkt->print());
+
+#if TRACING_ON
+ CacheBlk::State old_state = blk ? blk->status : 0;
#endif
-#endif //DOXYGEN_SHOULD_SKIP_THIS
+ Cycles latency = ticksToCycles(memSidePort.sendAtomic(bus_pkt));
+
+ bool is_invalidate = bus_pkt->isInvalidate();
+
+ // We are now dealing with the response handling
+ DPRINTF(Cache, "%s: Receive response: %s in state %i\n", __func__,
+ bus_pkt->print(), old_state);
+
+ // If packet was a forward, the response (if any) is already
+ // in place in the bus_pkt == pkt structure, so we don't need
+ // to do anything. Otherwise, use the separate bus_pkt to
+ // generate response to pkt and then delete it.
+ if (!is_forward) {
+ if (pkt->needsResponse()) {
+ assert(bus_pkt->isResponse());
+ if (bus_pkt->isError()) {
+ pkt->makeAtomicResponse();
+ pkt->copyError(bus_pkt);
+ } else if (pkt->cmd == MemCmd::WriteLineReq) {
+ // note the use of pkt, not bus_pkt here.
+
+ // write-line request to the cache that promoted
+ // the write to a whole line
+ blk = handleFill(pkt, blk, writebacks,
+ allocOnFill(pkt->cmd));
+ assert(blk != NULL);
+ is_invalidate = false;
+ satisfyRequest(pkt, blk);
+ } else if (bus_pkt->isRead() ||
+ bus_pkt->cmd == MemCmd::UpgradeResp) {
+ // we're updating cache state to allow us to
+ // satisfy the upstream request from the cache
+ blk = handleFill(bus_pkt, blk, writebacks,
+ allocOnFill(pkt->cmd));
+ satisfyRequest(pkt, blk);
+ maintainClusivity(pkt->fromCache(), blk);
+ } else {
+ // we're satisfying the upstream request without
+ // modifying cache state, e.g., a write-through
+ pkt->makeAtomicResponse();
+ }
+ }
+ delete bus_pkt;
+ }
+
+ if (is_invalidate && blk && blk->isValid()) {
+ invalidateBlock(blk);
+ }
+
+ return latency;
+}
+
+Tick
+Cache::recvAtomic(PacketPtr pkt)
+{
+ promoteWholeLineWrites(pkt);
+
+ return BaseCache::recvAtomic(pkt);
+}
+
+
+/////////////////////////////////////////////////////
+//
+// Response handling: responses from the memory side
+//
+/////////////////////////////////////////////////////
+
+
+void
+Cache::serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk,
+ PacketList &writebacks)
+{
+ MSHR::Target *initial_tgt = mshr->getTarget();
+ // First offset for critical word first calculations
+ const int initial_offset = initial_tgt->pkt->getOffset(blkSize);
+
+ const bool is_error = pkt->isError();
+ // allow invalidation responses originating from write-line
+ // requests to be discarded
+ bool is_invalidate = pkt->isInvalidate();
+
+ MSHR::TargetList targets = mshr->extractServiceableTargets(pkt);
+ for (auto &target: targets) {
+ Packet *tgt_pkt = target.pkt;
+ switch (target.source) {
+ case MSHR::Target::FromCPU:
+ Tick completion_time;
+ // Here we charge on completion_time the delay of the xbar if the
+ // packet comes from it, charged on headerDelay.
+ completion_time = pkt->headerDelay;
+
+ // Software prefetch handling for cache closest to core
+ if (tgt_pkt->cmd.isSWPrefetch()) {
+ // a software prefetch would have already been ack'd
+ // immediately with dummy data so the core would be able to
+ // retire it. This request completes right here, so we
+ // deallocate it.
+ delete tgt_pkt;
+ break; // skip response
+ }
+
+ // unlike the other packet flows, where data is found in other
+ // caches or memory and brought back, write-line requests always
+ // have the data right away, so the above check for "is fill?"
+ // cannot actually be determined until examining the stored MSHR
+ // state. We "catch up" with that logic here, which is duplicated
+ // from above.
+ if (tgt_pkt->cmd == MemCmd::WriteLineReq) {
+ assert(!is_error);
+ // we got the block in a writable state, so promote
+ // any deferred targets if possible
+ mshr->promoteWritable();
+ // NB: we use the original packet here and not the response!
+ blk = handleFill(tgt_pkt, blk, writebacks,
+ targets.allocOnFill);
+ assert(blk);
+
+ // discard the invalidation response
+ is_invalidate = false;
+ }
+
+ if (blk && blk->isValid() && !mshr->isForward) {
+ satisfyRequest(tgt_pkt, blk, true, mshr->hasPostDowngrade());
+
+ // How many bytes past the first request is this one
+ int transfer_offset =
+ tgt_pkt->getOffset(blkSize) - initial_offset;
+ if (transfer_offset < 0) {
+ transfer_offset += blkSize;
+ }
+
+ // If not critical word (offset) return payloadDelay.
+ // responseLatency is the latency of the return path
+ // from lower level caches/memory to an upper level cache or
+ // the core.
+ completion_time += clockEdge(responseLatency) +
+ (transfer_offset ? pkt->payloadDelay : 0);
+
+ assert(!tgt_pkt->req->isUncacheable());
+
+ assert(tgt_pkt->req->masterId() < system->maxMasters());
+ missLatency[tgt_pkt->cmdToIndex()][tgt_pkt->req->masterId()] +=
+ completion_time - target.recvTime;
+ } else if (pkt->cmd == MemCmd::UpgradeFailResp) {
+ // failed StoreCond upgrade
+ assert(tgt_pkt->cmd == MemCmd::StoreCondReq ||
+ tgt_pkt->cmd == MemCmd::StoreCondFailReq ||
+ tgt_pkt->cmd == MemCmd::SCUpgradeFailReq);
+ // responseLatency is the latency of the return path
+ // from lower level caches/memory to an upper level cache or
+ // the core.
+ completion_time += clockEdge(responseLatency) +
+ pkt->payloadDelay;
+ tgt_pkt->req->setExtraData(0);
+ } else {
+ // We are about to send a response to a cache above
+ // that asked for an invalidation; we need to
+ // invalidate our copy immediately as the most
+ // up-to-date copy of the block will now be in the
+ // cache above. It will also prevent this cache from
+ // responding (if the block was previously dirty) to
+ // snoops as they should snoop the caches above where
+ // they will get the response from.
+ if (is_invalidate && blk && blk->isValid()) {
+ invalidateBlock(blk);
+ }
+ // not a cache fill, just forwarding response
+ // responseLatency is the latency of the return path
+ // from lower level cahces/memory to the core.
+ completion_time += clockEdge(responseLatency) +
+ pkt->payloadDelay;
+ if (pkt->isRead() && !is_error) {
+ // sanity check
+ assert(pkt->getAddr() == tgt_pkt->getAddr());
+ assert(pkt->getSize() >= tgt_pkt->getSize());
+
+ tgt_pkt->setData(pkt->getConstPtr<uint8_t>());
+ }
+ }
+ tgt_pkt->makeTimingResponse();
+ // if this packet is an error copy that to the new packet
+ if (is_error)
+ tgt_pkt->copyError(pkt);
+ if (tgt_pkt->cmd == MemCmd::ReadResp &&
+ (is_invalidate || mshr->hasPostInvalidate())) {
+ // If intermediate cache got ReadRespWithInvalidate,
+ // propagate that. Response should not have
+ // isInvalidate() set otherwise.
+ tgt_pkt->cmd = MemCmd::ReadRespWithInvalidate;
+ DPRINTF(Cache, "%s: updated cmd to %s\n", __func__,
+ tgt_pkt->print());
+ }
+ // Reset the bus additional time as it is now accounted for
+ tgt_pkt->headerDelay = tgt_pkt->payloadDelay = 0;
+ cpuSidePort.schedTimingResp(tgt_pkt, completion_time, true);
+ break;
+
+ case MSHR::Target::FromPrefetcher:
+ assert(tgt_pkt->cmd == MemCmd::HardPFReq);
+ if (blk)
+ blk->status |= BlkHWPrefetched;
+ delete tgt_pkt;
+ break;
+
+ case MSHR::Target::FromSnoop:
+ // I don't believe that a snoop can be in an error state
+ assert(!is_error);
+ // response to snoop request
+ DPRINTF(Cache, "processing deferred snoop...\n");
+ // If the response is invalidating, a snooping target can
+ // be satisfied if it is also invalidating. If the reponse is, not
+ // only invalidating, but more specifically an InvalidateResp and
+ // the MSHR was created due to an InvalidateReq then a cache above
+ // is waiting to satisfy a WriteLineReq. In this case even an
+ // non-invalidating snoop is added as a target here since this is
+ // the ordering point. When the InvalidateResp reaches this cache,
+ // the snooping target will snoop further the cache above with the
+ // WriteLineReq.
+ assert(!is_invalidate || pkt->cmd == MemCmd::InvalidateResp ||
+ pkt->req->isCacheMaintenance() ||
+ mshr->hasPostInvalidate());
+ handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
+ break;
+
+ default:
+ panic("Illegal target->source enum %d\n", target.source);
+ }
+ }
+
+ maintainClusivity(targets.hasFromCache, blk);
+
+ if (blk && blk->isValid()) {
+ // an invalidate response stemming from a write line request
+ // should not invalidate the block, so check if the
+ // invalidation should be discarded
+ if (is_invalidate || mshr->hasPostInvalidate()) {
+ invalidateBlock(blk);
+ } else if (mshr->hasPostDowngrade()) {
+ blk->status &= ~BlkWritable;
+ }
+ }
+}
+
+PacketPtr
+Cache::evictBlock(CacheBlk *blk)
+{
+ PacketPtr pkt = (blk->isDirty() || writebackClean) ?
+ writebackBlk(blk) : cleanEvictBlk(blk);
+
+ invalidateBlock(blk);
+
+ return pkt;
+}
+
+void
+Cache::evictBlock(CacheBlk *blk, PacketList &writebacks)
+{
+ PacketPtr pkt = evictBlock(blk);
+ if (pkt) {
+ writebacks.push_back(pkt);
+ }
+}
+
+PacketPtr
+Cache::cleanEvictBlk(CacheBlk *blk)
+{
+ assert(!writebackClean);
+ assert(blk && blk->isValid() && !blk->isDirty());
+
+ // Creating a zero sized write, a message to the snoop filter
+ RequestPtr req = std::make_shared<Request>(
+ regenerateBlkAddr(blk), blkSize, 0, Request::wbMasterId);
+
+ if (blk->isSecure())
+ req->setFlags(Request::SECURE);
+
+ req->taskId(blk->task_id);
+
+ PacketPtr pkt = new Packet(req, MemCmd::CleanEvict);
+ pkt->allocate();
+ DPRINTF(Cache, "Create CleanEvict %s\n", pkt->print());
+
+ return pkt;
+}
+
+/////////////////////////////////////////////////////
+//
+// Snoop path: requests coming in from the memory side
+//
+/////////////////////////////////////////////////////
+
+void
+Cache::doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data,
+ bool already_copied, bool pending_inval)
+{
+ // sanity check
+ assert(req_pkt->isRequest());
+ assert(req_pkt->needsResponse());
+
+ DPRINTF(Cache, "%s: for %s\n", __func__, req_pkt->print());
+ // timing-mode snoop responses require a new packet, unless we
+ // already made a copy...
+ PacketPtr pkt = req_pkt;
+ if (!already_copied)
+ // do not clear flags, and allocate space for data if the
+ // packet needs it (the only packets that carry data are read
+ // responses)
+ pkt = new Packet(req_pkt, false, req_pkt->isRead());
+
+ assert(req_pkt->req->isUncacheable() || req_pkt->isInvalidate() ||
+ pkt->hasSharers());
+ pkt->makeTimingResponse();
+ if (pkt->isRead()) {
+ pkt->setDataFromBlock(blk_data, blkSize);
+ }
+ if (pkt->cmd == MemCmd::ReadResp && pending_inval) {
+ // Assume we defer a response to a read from a far-away cache
+ // A, then later defer a ReadExcl from a cache B on the same
+ // bus as us. We'll assert cacheResponding in both cases, but
+ // in the latter case cacheResponding will keep the
+ // invalidation from reaching cache A. This special response
+ // tells cache A that it gets the block to satisfy its read,
+ // but must immediately invalidate it.
+ pkt->cmd = MemCmd::ReadRespWithInvalidate;
+ }
+ // Here we consider forward_time, paying for just forward latency and
+ // also charging the delay provided by the xbar.
+ // forward_time is used as send_time in next allocateWriteBuffer().
+ Tick forward_time = clockEdge(forwardLatency) + pkt->headerDelay;
+ // Here we reset the timing of the packet.
+ pkt->headerDelay = pkt->payloadDelay = 0;
+ DPRINTF(CacheVerbose, "%s: created response: %s tick: %lu\n", __func__,
+ pkt->print(), forward_time);
+ memSidePort.schedTimingSnoopResp(pkt, forward_time, true);
+}
+
+uint32_t
+Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
+ bool is_deferred, bool pending_inval)
+{
+ DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
+ // deferred snoops can only happen in timing mode
+ assert(!(is_deferred && !is_timing));
+ // pending_inval only makes sense on deferred snoops
+ assert(!(pending_inval && !is_deferred));
+ assert(pkt->isRequest());
+
+ // the packet may get modified if we or a forwarded snooper
+ // responds in atomic mode, so remember a few things about the
+ // original packet up front
+ bool invalidate = pkt->isInvalidate();
+ bool M5_VAR_USED needs_writable = pkt->needsWritable();
+
+ // at the moment we could get an uncacheable write which does not
+ // have the invalidate flag, and we need a suitable way of dealing
+ // with this case
+ panic_if(invalidate && pkt->req->isUncacheable(),
+ "%s got an invalidating uncacheable snoop request %s",
+ name(), pkt->print());
+
+ uint32_t snoop_delay = 0;
+
+ if (forwardSnoops) {
+ // first propagate snoop upward to see if anyone above us wants to
+ // handle it. save & restore packet src since it will get
+ // rewritten to be relative to cpu-side bus (if any)
+ bool alreadyResponded = pkt->cacheResponding();
+ if (is_timing) {
+ // copy the packet so that we can clear any flags before
+ // forwarding it upwards, we also allocate data (passing
+ // the pointer along in case of static data), in case
+ // there is a snoop hit in upper levels
+ Packet snoopPkt(pkt, true, true);
+ snoopPkt.setExpressSnoop();
+ // the snoop packet does not need to wait any additional
+ // time
+ snoopPkt.headerDelay = snoopPkt.payloadDelay = 0;
+ cpuSidePort.sendTimingSnoopReq(&snoopPkt);
+
+ // add the header delay (including crossbar and snoop
+ // delays) of the upward snoop to the snoop delay for this
+ // cache
+ snoop_delay += snoopPkt.headerDelay;
+
+ if (snoopPkt.cacheResponding()) {
+ // cache-to-cache response from some upper cache
+ assert(!alreadyResponded);
+ pkt->setCacheResponding();
+ }
+ // upstream cache has the block, or has an outstanding
+ // MSHR, pass the flag on
+ if (snoopPkt.hasSharers()) {
+ pkt->setHasSharers();
+ }
+ // If this request is a prefetch or clean evict and an upper level
+ // signals block present, make sure to propagate the block
+ // presence to the requester.
+ if (snoopPkt.isBlockCached()) {
+ pkt->setBlockCached();
+ }
+ // If the request was satisfied by snooping the cache
+ // above, mark the original packet as satisfied too.
+ if (snoopPkt.satisfied()) {
+ pkt->setSatisfied();
+ }
+ } else {
+ cpuSidePort.sendAtomicSnoop(pkt);
+ if (!alreadyResponded && pkt->cacheResponding()) {
+ // cache-to-cache response from some upper cache:
+ // forward response to original requester
+ assert(pkt->isResponse());
+ }
+ }
+ }
+
+ bool respond = false;
+ bool blk_valid = blk && blk->isValid();
+ if (pkt->isClean()) {
+ if (blk_valid && blk->isDirty()) {
+ DPRINTF(CacheVerbose, "%s: packet (snoop) %s found block: %s\n",
+ __func__, pkt->print(), blk->print());
+ PacketPtr wb_pkt = writecleanBlk(blk, pkt->req->getDest(), pkt->id);
+ PacketList writebacks;
+ writebacks.push_back(wb_pkt);
+
+ if (is_timing) {
+ // anything that is merely forwarded pays for the forward
+ // latency and the delay provided by the crossbar
+ Tick forward_time = clockEdge(forwardLatency) +
+ pkt->headerDelay;
+ doWritebacks(writebacks, forward_time);
+ } else {
+ doWritebacksAtomic(writebacks);
+ }
+ pkt->setSatisfied();
+ }
+ } else if (!blk_valid) {
+ DPRINTF(CacheVerbose, "%s: snoop miss for %s\n", __func__,
+ pkt->print());
+ if (is_deferred) {
+ // we no longer have the block, and will not respond, but a
+ // packet was allocated in MSHR::handleSnoop and we have
+ // to delete it
+ assert(pkt->needsResponse());
+
+ // we have passed the block to a cache upstream, that
+ // cache should be responding
+ assert(pkt->cacheResponding());
+
+ delete pkt;
+ }
+ return snoop_delay;
+ } else {
+ DPRINTF(Cache, "%s: snoop hit for %s, old state is %s\n", __func__,
+ pkt->print(), blk->print());
+
+ // We may end up modifying both the block state and the packet (if
+ // we respond in atomic mode), so just figure out what to do now
+ // and then do it later. We respond to all snoops that need
+ // responses provided we have the block in dirty state. The
+ // invalidation itself is taken care of below. We don't respond to
+ // cache maintenance operations as this is done by the destination
+ // xbar.
+ respond = blk->isDirty() && pkt->needsResponse();
+
+ chatty_assert(!(isReadOnly && blk->isDirty()), "Should never have "
+ "a dirty block in a read-only cache %s\n", name());
+ }
+
+ // Invalidate any prefetch's from below that would strip write permissions
+ // MemCmd::HardPFReq is only observed by upstream caches. After missing
+ // above and in it's own cache, a new MemCmd::ReadReq is created that
+ // downstream caches observe.
+ if (pkt->mustCheckAbove()) {
+ DPRINTF(Cache, "Found addr %#llx in upper level cache for snoop %s "
+ "from lower cache\n", pkt->getAddr(), pkt->print());
+ pkt->setBlockCached();
+ return snoop_delay;
+ }
+
+ if (pkt->isRead() && !invalidate) {
+ // reading without requiring the line in a writable state
+ assert(!needs_writable);
+ pkt->setHasSharers();
+
+ // if the requesting packet is uncacheable, retain the line in
+ // the current state, otherwhise unset the writable flag,
+ // which means we go from Modified to Owned (and will respond
+ // below), remain in Owned (and will respond below), from
+ // Exclusive to Shared, or remain in Shared
+ if (!pkt->req->isUncacheable())
+ blk->status &= ~BlkWritable;
+ DPRINTF(Cache, "new state is %s\n", blk->print());
+ }
+
+ if (respond) {
+ // prevent anyone else from responding, cache as well as
+ // memory, and also prevent any memory from even seeing the
+ // request
+ pkt->setCacheResponding();
+ if (!pkt->isClean() && blk->isWritable()) {
+ // inform the cache hierarchy that this cache had the line
+ // in the Modified state so that we avoid unnecessary
+ // invalidations (see Packet::setResponderHadWritable)
+ pkt->setResponderHadWritable();
+
+ // in the case of an uncacheable request there is no point
+ // in setting the responderHadWritable flag, but since the
+ // recipient does not care there is no harm in doing so
+ } else {
+ // if the packet has needsWritable set we invalidate our
+ // copy below and all other copies will be invalidates
+ // through express snoops, and if needsWritable is not set
+ // we already called setHasSharers above
+ }
+
+ // if we are returning a writable and dirty (Modified) line,
+ // we should be invalidating the line
+ panic_if(!invalidate && !pkt->hasSharers(),
+ "%s is passing a Modified line through %s, "
+ "but keeping the block", name(), pkt->print());
+
+ if (is_timing) {
+ doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
+ } else {
+ pkt->makeAtomicResponse();
+ // packets such as upgrades do not actually have any data
+ // payload
+ if (pkt->hasData())
+ pkt->setDataFromBlock(blk->data, blkSize);
+ }
+ }
+
+ if (!respond && is_deferred) {
+ assert(pkt->needsResponse());
+ delete pkt;
+ }
+
+ // Do this last in case it deallocates block data or something
+ // like that
+ if (blk_valid && invalidate) {
+ invalidateBlock(blk);
+ DPRINTF(Cache, "new state is %s\n", blk->print());
+ }
+
+ return snoop_delay;
+}
+
+
+void
+Cache::recvTimingSnoopReq(PacketPtr pkt)
+{
+ DPRINTF(CacheVerbose, "%s: for %s\n", __func__, pkt->print());
+
+ // no need to snoop requests that are not in range
+ if (!inRange(pkt->getAddr())) {
+ return;
+ }
+
+ bool is_secure = pkt->isSecure();
+ CacheBlk *blk = tags->findBlock(pkt->getAddr(), is_secure);
+
+ Addr blk_addr = pkt->getBlockAddr(blkSize);
+ MSHR *mshr = mshrQueue.findMatch(blk_addr, is_secure);
+
+ // Update the latency cost of the snoop so that the crossbar can
+ // account for it. Do not overwrite what other neighbouring caches
+ // have already done, rather take the maximum. The update is
+ // tentative, for cases where we return before an upward snoop
+ // happens below.
+ pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay,
+ lookupLatency * clockPeriod());
+
+ // Inform request(Prefetch, CleanEvict or Writeback) from below of
+ // MSHR hit, set setBlockCached.
+ if (mshr && pkt->mustCheckAbove()) {
+ DPRINTF(Cache, "Setting block cached for %s from lower cache on "
+ "mshr hit\n", pkt->print());
+ pkt->setBlockCached();
+ return;
+ }
+
+ // Bypass any existing cache maintenance requests if the request
+ // has been satisfied already (i.e., the dirty block has been
+ // found).
+ if (mshr && pkt->req->isCacheMaintenance() && pkt->satisfied()) {
+ return;
+ }
+
+ // Let the MSHR itself track the snoop and decide whether we want
+ // to go ahead and do the regular cache snoop
+ if (mshr && mshr->handleSnoop(pkt, order++)) {
+ DPRINTF(Cache, "Deferring snoop on in-service MSHR to blk %#llx (%s)."
+ "mshrs: %s\n", blk_addr, is_secure ? "s" : "ns",
+ mshr->print());
+
+ if (mshr->getNumTargets() > numTarget)
+ warn("allocating bonus target for snoop"); //handle later
+ return;
+ }
+
+ //We also need to check the writeback buffers and handle those
+ WriteQueueEntry *wb_entry = writeBuffer.findMatch(blk_addr, is_secure);
+ if (wb_entry) {
+ DPRINTF(Cache, "Snoop hit in writeback to addr %#llx (%s)\n",
+ pkt->getAddr(), is_secure ? "s" : "ns");
+ // Expect to see only Writebacks and/or CleanEvicts here, both of
+ // which should not be generated for uncacheable data.
+ assert(!wb_entry->isUncacheable());
+ // There should only be a single request responsible for generating
+ // Writebacks/CleanEvicts.
+ assert(wb_entry->getNumTargets() == 1);
+ PacketPtr wb_pkt = wb_entry->getTarget()->pkt;
+ assert(wb_pkt->isEviction() || wb_pkt->cmd == MemCmd::WriteClean);
+
+ if (pkt->isEviction()) {
+ // if the block is found in the write queue, set the BLOCK_CACHED
+ // flag for Writeback/CleanEvict snoop. On return the snoop will
+ // propagate the BLOCK_CACHED flag in Writeback packets and prevent
+ // any CleanEvicts from travelling down the memory hierarchy.
+ pkt->setBlockCached();
+ DPRINTF(Cache, "%s: Squashing %s from lower cache on writequeue "
+ "hit\n", __func__, pkt->print());
+ return;
+ }
+
+ // conceptually writebacks are no different to other blocks in
+ // this cache, so the behaviour is modelled after handleSnoop,
+ // the difference being that instead of querying the block
+ // state to determine if it is dirty and writable, we use the
+ // command and fields of the writeback packet
+ bool respond = wb_pkt->cmd == MemCmd::WritebackDirty &&
+ pkt->needsResponse();
+ bool have_writable = !wb_pkt->hasSharers();
+ bool invalidate = pkt->isInvalidate();
+
+ if (!pkt->req->isUncacheable() && pkt->isRead() && !invalidate) {
+ assert(!pkt->needsWritable());
+ pkt->setHasSharers();
+ wb_pkt->setHasSharers();
+ }
+
+ if (respond) {
+ pkt->setCacheResponding();
+
+ if (have_writable) {
+ pkt->setResponderHadWritable();
+ }
+
+ doTimingSupplyResponse(pkt, wb_pkt->getConstPtr<uint8_t>(),
+ false, false);
+ }
+
+ if (invalidate && wb_pkt->cmd != MemCmd::WriteClean) {
+ // Invalidation trumps our writeback... discard here
+ // Note: markInService will remove entry from writeback buffer.
+ markInService(wb_entry);
+ delete wb_pkt;
+ }
+ }
+
+ // If this was a shared writeback, there may still be
+ // other shared copies above that require invalidation.
+ // We could be more selective and return here if the
+ // request is non-exclusive or if the writeback is
+ // exclusive.
+ uint32_t snoop_delay = handleSnoop(pkt, blk, true, false, false);
+
+ // Override what we did when we first saw the snoop, as we now
+ // also have the cost of the upwards snoops to account for
+ pkt->snoopDelay = std::max<uint32_t>(pkt->snoopDelay, snoop_delay +
+ lookupLatency * clockPeriod());
+}
+
+Tick
+Cache::recvAtomicSnoop(PacketPtr pkt)
+{
+ // no need to snoop requests that are not in range.
+ if (!inRange(pkt->getAddr())) {
+ return 0;
+ }
+
+ CacheBlk *blk = tags->findBlock(pkt->getAddr(), pkt->isSecure());
+ uint32_t snoop_delay = handleSnoop(pkt, blk, false, false, false);
+ return snoop_delay + lookupLatency * clockPeriod();
+}
+
+bool
+Cache::isCachedAbove(PacketPtr pkt, bool is_timing)
+{
+ if (!forwardSnoops)
+ return false;
+ // Mirroring the flow of HardPFReqs, the cache sends CleanEvict and
+ // Writeback snoops into upper level caches to check for copies of the
+ // same block. Using the BLOCK_CACHED flag with the Writeback/CleanEvict
+ // packet, the cache can inform the crossbar below of presence or absence
+ // of the block.
+ if (is_timing) {
+ Packet snoop_pkt(pkt, true, false);
+ snoop_pkt.setExpressSnoop();
+ // Assert that packet is either Writeback or CleanEvict and not a
+ // prefetch request because prefetch requests need an MSHR and may
+ // generate a snoop response.
+ assert(pkt->isEviction() || pkt->cmd == MemCmd::WriteClean);
+ snoop_pkt.senderState = nullptr;
+ cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
+ // Writeback/CleanEvict snoops do not generate a snoop response.
+ assert(!(snoop_pkt.cacheResponding()));
+ return snoop_pkt.isBlockCached();
+ } else {
+ cpuSidePort.sendAtomicSnoop(pkt);
+ return pkt->isBlockCached();
+ }
+}
+
+bool
+Cache::sendMSHRQueuePacket(MSHR* mshr)
+{
+ assert(mshr);
+
+ // use request from 1st target
+ PacketPtr tgt_pkt = mshr->getTarget()->pkt;
+
+ if (tgt_pkt->cmd == MemCmd::HardPFReq && forwardSnoops) {
+ DPRINTF(Cache, "%s: MSHR %s\n", __func__, tgt_pkt->print());
+
+ // we should never have hardware prefetches to allocated
+ // blocks
+ assert(!tags->findBlock(mshr->blkAddr, mshr->isSecure));
+
+ // We need to check the caches above us to verify that
+ // they don't have a copy of this block in the dirty state
+ // at the moment. Without this check we could get a stale
+ // copy from memory that might get used in place of the
+ // dirty one.
+ Packet snoop_pkt(tgt_pkt, true, false);
+ snoop_pkt.setExpressSnoop();
+ // We are sending this packet upwards, but if it hits we will
+ // get a snoop response that we end up treating just like a
+ // normal response, hence it needs the MSHR as its sender
+ // state
+ snoop_pkt.senderState = mshr;
+ cpuSidePort.sendTimingSnoopReq(&snoop_pkt);
+
+ // Check to see if the prefetch was squashed by an upper cache (to
+ // prevent us from grabbing the line) or if a Check to see if a
+ // writeback arrived between the time the prefetch was placed in
+ // the MSHRs and when it was selected to be sent or if the
+ // prefetch was squashed by an upper cache.
+
+ // It is important to check cacheResponding before
+ // prefetchSquashed. If another cache has committed to
+ // responding, it will be sending a dirty response which will
+ // arrive at the MSHR allocated for this request. Checking the
+ // prefetchSquash first may result in the MSHR being
+ // prematurely deallocated.
+ if (snoop_pkt.cacheResponding()) {
+ auto M5_VAR_USED r = outstandingSnoop.insert(snoop_pkt.req);
+ assert(r.second);
+
+ // if we are getting a snoop response with no sharers it
+ // will be allocated as Modified
+ bool pending_modified_resp = !snoop_pkt.hasSharers();
+ markInService(mshr, pending_modified_resp);
+
+ DPRINTF(Cache, "Upward snoop of prefetch for addr"
+ " %#x (%s) hit\n",
+ tgt_pkt->getAddr(), tgt_pkt->isSecure()? "s": "ns");
+ return false;
+ }
+
+ if (snoop_pkt.isBlockCached()) {
+ DPRINTF(Cache, "Block present, prefetch squashed by cache. "
+ "Deallocating mshr target %#x.\n",
+ mshr->blkAddr);
+
+ // Deallocate the mshr target
+ if (mshrQueue.forceDeallocateTarget(mshr)) {
+ // Clear block if this deallocation resulted freed an
+ // mshr when all had previously been utilized
+ clearBlocked(Blocked_NoMSHRs);
+ }
+
+ // given that no response is expected, delete Request and Packet
+ delete tgt_pkt;
+
+ return false;
+ }
+ }
+
+ return BaseCache::sendMSHRQueuePacket(mshr);
+}
+
+Cache*
+CacheParams::create()
+{
+ assert(tags);
+ assert(replacement_policy);
+
+ return new Cache(this);
+}
projects / gem5.git / blobdiff